Sentinel's Gaze

You can check out this optional dungeon for additional loot and valuables. Though, full exploration won't be possible until you acquire the Soul Splitter ability. Before entering the dungeon, check the wall to your left (north) behind a thorn to find a Boatman Coin. Enter the dungeon afterward.

Head downstairs and wall-run to wallpost. Climb down a bit then look to the left to find a chest. Wall-run to reach and loot it, then backtrack to the post and continue downstairs until you reach the door. Move forth and destroy all enemies in sight. Once clear, grab the Boatman Coin in the area's northeast corner.

Climb the northwest platform and find a Relic of Etu-Goth behind a torch near the edge of the platform. Grab a shadowbomb and use it to destroy the crystals below. Loot the chest inside and destroy the weapon racks to obtain random weapons.

After acquiring Soul SPlitter

When you acquired the Soul Splitter ability, you can loot the rest of this location. See Entering Boneriven on how to do this.